1. Field of the Invention
The invention relates to an analog-to-digital converter for outputting a digital signal corresponding to an analog signal.
2. Description of the Prior Art
When an analog-to-digital converter (hereinafter, also referred to as an A-D converter) converts an analog signal to a digital signal, conversion accuracy may be degraded by an external factor (noise). In order to remove the influence of noise of an input analog signal, a known A-D converter samples an analog data signal an even number of times at intervals equal to a half of a period of an alternating current component superimposing on the analog signal, and adds the sampling results (for example, Japanese Patent Laid-Open Publication No. 9-55658).
Noise removal of this A-D converter is effective for noise that superimposes on an input analog signal, but is not effective when noise is generated within the A-D converter.